Thermodynamics of Hydrogen Desorption from NaMgH₃ and Its Application As a Solar Heat Storage Medium

NaMgH3 has been considered as a potential hydrogen storage material and is an intermediary phase in a number of complex-hydride destabilization reactions. Using careful pressure−composition−isotherm measurements, the hydrogen equilibrium plateau was shown to be flat with negligible hysteresis. The enthalpy of desorption, ΔH, was found to be 86.6 ± 1.0 kJ/(mol H2) and the entropy, ΔS, to be 132.2 ± 1.3 J/(mol H2 K), values lower than previously reported. The high enthalpy, flat plateau, and lack of hysteresis make NaMgH3 a potential candidate as a solar heat storage medium.